Marana bridges to be fitted with bat 'condos'

The locations, though — under bridges over the Santa Cruz River on North Cortaro and West Ina Roads — are less than desirable. And the space — about 38 inches long and 20 inches wide — is a bit cramped.

But the accommodations should be just fine, as long as you happen to be a part of the estimated tens of thousands of bats that frequent the bridges.

A proposal for two Marana "bat condo" projects has been approved by the Regional Transportation Authority's Wildlife Linkages Committee and Transportation Improvement Program Subcommittee.

"Bridges are really important for a number of species of bats," University of Arizona bat biologist Ted Fleming said. "I think the plan is a win-win for bat conservation, for sure."

Shawn Lowery of the Arizona Game and Fish Department said the project will be crucial for the state's bat population.

"We will be losing habitat if we do not start doing things more proactively to support the bat population," Lowery said.

More than 30,000 bats are believed to roost near the Ina Road Bridge during the summer, including the Mexican free-tailed bat and the cave myotis. This project provides mitigation for bat habitat that will be removed when the existing Ina Road Bridge is demolished, possibly in 2016.

Janine Spencer, environmental projects coordinator at Marana's Environmental Engineering department, along with other bat biologists, has studied the bat populations and delivered a presentation to the RTA in August that demonstrated the importance of the structures for the bats.

The first leg, slated for the spring, will be the addition of two structures under the Cortaro bridge. The RTA is paying for the project, which totals $80,000. The town of Marana and Arizona Game and Fish Department are providing in-kind contributions.

The Cortaro Road Bridge condos, which come from Texas-based manufacturer Maberry, each hold about 2,000 bats. The condos are meant to give some of the bats a place to roost when the Ina Road Bridge project disturbs their current habitat.

The shells of the 26-inch tall, 20-inch wide and 38-inch long condos are made of galvanized steel, which is insulated to keep temperatures stable. Each condo is equipped with attic space and vents to keep air flowing.

"I'm really looking forward to putting these in, seeing how they're used and how long it takes in post-construction monitoring to see what species of bats use it," Spencer said. "Which numbers, during which seasons."

The proposal also includes integrating bat condos into a construction project on the Ina Road Bridge.

That portion of the project, which includes logging bat population and activities in the area, is projected to cost $40,018, and will integrate nine bat crevice structures into the construction of the side of the bridge that carries eastbound traffic. These larger structures will be 14 inches deep and 48 inches long.

To accommodate the extra depth needed for the bat roosts, decks in those areas will be widened to 23 inches from the standard 8 inches.

Slats between roost openings will be made of concrete backerboard to help with insulation, with varying width between each slat to give the openings different looks, giving the bats options to choose where to roost, Spencer said.

"What I'm hoping is this catches on with some older bridges in the Tucson area," Spencer said.

"I'm hoping this will act sort of as a template for what works with these bridges — something simple and straightforward that other jurisdictions can use."